1. Field of the Invention
The invention pertains to a seal with high temperature and high wear resistance and to the particular application of the seal in a combustor for a gas turbine or between blade platforms in a gas turbine.
2. Brief Description of the Related Art
Seals applied in high temperature environments such as in combustors for gas turbines, in industrial gas turbine technology, steam turbine technology, and aerospace technology are required to withstand high temperatures for a given time duration. In many cases, due to vibrations present in such systems, they are also required to provide a seal over a varying distance and a high wear resistance.
A combustor for a gas turbine includes thermal protection liners placed along the inner circumference of the inner wall of the combustor casing. Such a combustor typically has a conical or a cylindrical shape. The liners are arranged in segments along the inner wall. The temperatures within the combustor rise up to 1200 or 1400° C., such that the liner segments and casing wall must be cooled in order to ensure a significant lifetime. A cooling is realized, for example, by the circulation of air that is between the inner casing wall and the liner segments. In order to control the flow of cooling medium and/or limit the volume of necessary cooling medium (because the cooling medium is costly), seals are placed between adjacent liner segments. In a gas turbine for power generation or aircrafts, the cooling medium can be air or steam.
Large vibrations occur in combustors for gas turbines during operation and in particular during operation at low emission levels. For this reason, spring loaded seals are used as they provide a sealing effect over a large range about a nominal distance. In order to withstand the rubbing against adjacent components, they are furthermore provided with a wear resistant coating. The lifetime of such seals is either determined by the lifetime of the coating, which is the time, in which the coating rubs off mechanically or is depleted as a result of other factors such as oxidation and/or corrosion.
A further problem encountered in the design of such seals is the limited time, for which materials maintain a spring load during exposure to elevated temperatures.
In a gas turbine seals are applied between platforms for stationary blades or stator blades in order to seal the hot gas region from cooling regions for the blades. High performance seals are required in order to minimise the cooling fluid volume and to prevent any hot gas from entering the cooling passages. Such seals must withstand the high prevalent temperatures in the gas turbine as well as perform in situations with large vibrations and large thermal expansions of individual components.
EP 1 306 589 discloses an annular high temperature seal intended for resistance to high temperature stress relaxation. It includes one component having either a single layer or a two-layered system, where the two layers extend over the entire length of the seal. The material or materials for this one component are one of solid solution hardened alloys, precipitation hardened metallic alloys, or dispersion hardened alloys.
U.S. Pat. No. 3,761,102 discloses a sealing ring, in particular a gasket or washer, shaped in a “C” in cross-section with a spring member placed between the inner arms of the “C”.